Circuit interrupter



Feb. 13, 1962 J. D. COBINE ETAL 3,021,409

CIRCUIT INTERRUPTER Filed Sept. 24. 1959 5 Fig]. 5 'F'l'gj.

In V2 2'? tor-s: dame: D. Cob/me,

Newe C. Coo/f,

7' air-A ttor'n ey.

United States Patent 3,021,409 CIRCUIT INTERRUPTER James D. Cobine,Rexford, and Newcll C. Cook, Schenectady, N.Y., assignors to GeneralElectric Company, a corporation of New York Filed Sept. 24, 1959, Ser.No. 842,011

Claims. (Cl. 200-149) Our invention relates to an improved circuitinterrupter.v While not limited thereto, the present invention relatesparticularly to surge voltage protectors for alternating currentdistribution systems and gas type circuit breakers or interrupters forsuch systems.

In surge voltage protectors for alternating current sysor interrupterposes a similar operational problem. Here the average circuit openingoperation involves separation of the electrode contact faces whilecurrent is flowing, and hence, the creation of an arc. The are isfrequently maintained for a very considerable portion of the alternatingcurrent half-cycle. It is usually not possible-and indeed it isfrequently undesirableto interrupt the arc prior to the next occurringcurrent zero. However, when the instantaneous current does reach a zero(whether the first following electrode separation or some subsequentzero), it is important to assure positively that the are is not restruckwhen the voltage recovers.

In accord with the present invention, the unusual volt age recoveryproperties of silicon. tetrafluoride and the characteristics of metalsilica-fluoride double salts are utilized to provide highly effectivesurge voltage protector and gas circuit breaker or interrupteroperation. The silicon tetrafluoride gas is characterized by a veryrapid recovery of dielectric strength following arcing. While the arcexists, the gas provides conduction carriers for the electric current.However, when the arc. current flow goes to zero, this gas very abruptlyloses its conducting capabilities and very quickly forms a medium ofrelatively high dielectric strength. In an actual surge voltageprotector or circuit breaker constructed in accord with the presentinvention, the effective length of the are through the silicontetrafluoride gas is madeof sufficient length to define a rate ofelectric strength recovery exceeding the rate of recovery of systemvoltage. This assures that the arc is not restruck. I

Further in accord with the present invention, the silicon tetrafluoridegas is formed by the action of the arc itself upon a non-conductingmetal silico-fiuoride located within the zone of thermal influence ofthe arc. The required silicon tetrafluoride gas is thus formed by theplay of the are upon the metal silica-fluoride, this action serving todecompose the metal silico-fluoride into the silicon tetrafluoride. Theparticular metal silico-fluoride may be any one of a variety of metals.For commercial and other reasons cuprous silico-fluoride (CuSiF ispreferred. The silico-fluoride may be located on or be a part of thearcing surfaces of the electrodes, it may be a separate body within thezone of influence of the are, it may be a component of the glaze used onan insulator over which the arc plays, or it may be otherwise located torespond to the arc by the production of silicon tetrafluoride.

3,021,409 Patented Feb. 13, 1962 In accord witha specific embodiment ofthe present invention, the interrupter is defined by electrodes locatedwithin a substantially enclosed chamber. If desired, the chamber can becompletely enclosed and filled with a gas providing a particularly highnormal dielectric strength. Alternatively, the enclosure may beincomplete and air may be used as the initial gas. In either event, thesilicon tetrafluoride formed by the arc remains generally in theychamber after arc extinction. Over a subsequent period of time itrecombines with the residual metal fluoride formed when the silicontetratluoride is generated. In substantial measure the metalsilico-fluoride is thereby regenerated and the unit conditioned forfurther operations. In one embodiment of this form of the structure, theelectrodes themselves are a repository of metal silicofluorides so thatthe reformed metal silico-fluoride is on the electrodes .and isnecessarily physically located so as to be subject to the influence ofthe arc, and hence become the source of silicon tetrafluoride forfurther interruptions. I It is, therefore, an object of the presentinvention to provide an improved circuit interrupter utilizing the usualproperties of silicon tetrafluoride.

A further object of the present invention is to provide a circuitinterrupter using silicon tetrafluoride and in which the currentinterrupted generates the required silicon tetrafluoride gas.

Another object of the present inventionis to provide a circuitinterrupter using silicon tetrafluoride gas in which it is unnecessaryto surround the arc-electrodes with silicon tetrafluoride gas inagas-tight chamber.

Still another object of the presentinvention is to provide an improvedcircuit interrupter in which a metal vide a circuit interrupterespecially suitable for use as a surge voltage protector where, ceramicinsulating surfaces such as insulator. strings are subjected to thethermal influence of thearc.

Yet another object of the present invention is to provide a circuitinterrupter especially suitable for use with I an air or other gascircuit breaker in which the arc initially formed between separatingcontacts is propelled against arc-quenching surfaces.

, The novel features which we believe to be characteristic of ourinvention are set forth with particularity in the appended claims. Ourinvention itself, however, both i understood by reference to thefollowing description taken in connection with theaccompanying drawings,in which: FIG. 1 is a diagrammatic view of a circuit interrupter oftheexpulsion type constructed in accordance with the present invention;

FIG. 2 is an alternative embodiment of the circuit interrupter of FIG.1; I I

FIG. 3 is a view of an insulator string with arcing 'rings defining asurge voltage protector in accordance with the present invention; and II FIG. 4 is a cross-sectional view of an enclosed surge voltageprotector constructed in accordance with the present invention.

Referring now to FIG. 1, there is shown in a. somewhat diagrammatic viewa circuit interrupter of the gas type. In the form shown, theinterrupter is of the airbreak expulsion type. In this type ofinterrupter, the

,arc is drawn into a narrow channel or "tube composed and is connectedby lug 4 to one conductor 5 of the connected electric system. The otherelectrode 2 is in the form of a finger. it is also of a suitableconducting material such as copper. Electrode 2 at its end 2a is roundedto be received in the mating cup-like recess in of the upper electrode 1to form an effective current conducting path.

The electrode 2 is movably supported by suitable means (not shown). itis connected to a conductor 6 of the connected electrode system by theconnector 7, which may be of any suitable form not interfering with theup and down movement of the electrode 2. In a typical application of aninterrupter of this form, the conductors 5 and 6, together with theelectrodes 1 and 2, may be in series with an electric system load. Insuch application, the actuating mechanism (which may include a fusibleelement) pulls the conductor 2 from the contactmaking to thecontact-breaking position of FIG. 1 in response to excessive loadcurrent.

As shown in HS. 1, the sleeve 3 is embedded in and protrudes from theupper electrode 1. This sleeve has a longitudinal bore 8 which receivesthe movable electrode 2 with a small annular clearance space. Normally,this sleeve is made of a material that generates copious quantities ofgas under the influence of an are drawn as the electrode 2 is broughtdown out of contact with the electrode 1. This gas tends to serve as acoolant and to aid in quenching the arc.

in accordance with the form of the present-invention shown in PEG. 1,the sleeve 3 has at least its inside surface including a silico-fluoridematerial. That is, a material that contains a metallic silico-fiuoride.Such material may, for example, be incorporated in the mate rial fromwhich the entire sleeve 3 is made. Alternatively, it may be incorporatedin a resin paint or coating that is applied to the inside surface of thesleeve and subsequently hat-dens. In still another construction, thesleeve 3 may be of ceramic material and the inner bore 8 coated with aglaze containing silico-fiuon'de material.

Many metal silico-fiuoride double salts may be used as thesilicofiuoride material. Cuprous silico-fiuoride (CuSiF is especiallyuseful because it has a favorable ionizing potential and is commerciallyavailable at a reasonable price. Other suitable materials includecalcium silico-fluoride (CaSiF barium silico-fluoride (BaSiF sodiumsilico-fluoride (Na SiF ammonium silico-lluoride ((NHQ SiF and leadsilico-fluoride (PbSiF These and other metal silico-fiuoride doublesalts have the characteristic of decomposing under the influence of theelectric arc. The decomposition products include silicon tetrafluoride(Silk), a gas under the conditions of the arc.

Like all the other gases in the are, the silicon tetrailuoride ionizesand thus provides conduction carriers for the current. However, this gashas the unusual characteristic of providing a very rapid dielectricrecovery voltage upon arc inten'uption. In an exceedingly short timeafter arc quench, a space containing a substantial quantity of silicontetrafluoride deionizes and defines a space of substantial dielectricstrength. An apparatus such as that of FIG. 1 thereby is capable ofwithstanding a very rapidly increasing applied voltage following areextinction and may be applied to an electric system with a rapid voltagerecovery following a current interruption.

'FIG. 2 shows an alternative form of the structure of FIG. 1. In thisform the upper electrode 1 is impregnated with a silico-fluoridematerial. Since the arc plays upon the electrode surface, this materialdecomposes to generate silicon tetrafluoride in the same fashion abovedescribed with reference to sleeve 3. If desired, the movable electrode2 could be so impregnated in lieu of or in addition to electrode 1. Itis preferred that at least electrade 1 be so impregnated so that thesilicon tetrafluoride gas evolved will tend to sweep over the space ofthe are before discharging into the atmosphere.

FIG. 3 shows a transmission line conductor 9 carried by support arm 10through the insulator string and surge voltage protector 11. Theinsulator string is made up of a group of connected insulators of theconventional porcelain type capable of sustaining the weight of theconductor 9. These are glazed with a material containing asilico-fluoride double salt, such as cuprous silicofiuoride. The arcingrings 13 are provided to form points of comparatively high electricfield gradient between which the arc is initially struck in the event ofan overvoltage on the line conductor 9.

In the event of an are between the arcing rings 13, FIG. 3, the arequickly envelops the insulators 12 and plays upon them. Silicontetrafluoride evolves from the glaze on the insulators 12 under thisaction of the arc. The arcing space is thus occupied by silicontetrafiuoride gas and rapidly recovers its dielectric strength when thesurge voltage disappears and the current zero takes place.

FIG. 4 shows still another embodiment of the present invention asapplied to a surge voltage protector. In this instance, a pair ofelectrodes 15 are located in spaced relationship in the envelope l4 andhave hook portions 16 outside the envelope for attachment to the circuitterminals to be protected. The envelope 14 is of any suitable insulatingmaterial defining a closed space. Either the electrodes 15 or some otherportion of the unit subjected to the influence of the arc is impregnatedor coated with a metal silico-fiuoride double salt, such as cuproussilico-fiuoride. In the event or" a voltage surge, arcing takes placebetween electrodes 15, the metal silico-fluoride decomposes to formsilicon tetrafiuoride, and when the current is ultimately interruptedthe silicon tetrafiuoride defines a space of rapid dielectric strengthrecovery to withstand the system recovery voltage applied between theelectrodes.

The closed device of FIG. 4 is essentially completely self-regeneratingWhen the arc is interrupted, the silicon tetrafiuoride in the containerenvelope begins a process of reuniting with whatever metal it contacts.In a structure similar to FIG. 4, where essentially all of the exposedmetal is also subjected to the are, essentially all the resulting metalsilieo-fiuoride double salt becomes available to generate siliconfluoride upon the next arc interruption. This regenerative feature isprovided to a substantial degree in structures like those of FIGS. 1 and2, where a substantial quantity of the silicon tetratluoride recombineswith exposed residual electrode materials. It is most effectivelyobtained, however, in a completely closed system such as that of FIG. 4.

While silicon tetrafiuoride provides a rapid dielectric strengthrecovery, the ultimate dielectric strength of this gas is of the sameorder of magnitude as air. In a closed device such as that of FIG. 4,the ultimate dielectric strength of this gas is of the same order ofmagnitude as air. In a closed device such as that of FIG. 4, theultimate dielectric strength can be somewhat increased by incorporatinga gas of greater dielectric strength. One such gas is sulfurhexafluoride (SP With a gas of the type in the envelope 14, the normalbreakdown strength of the protector is determined by the dielectricstrength of this gas and the rate of dielectric strength recoveryfollowing are interruption is determined largely by the action of thesilicon tetrafluoride.

If desired, the envelope 14 of FIG. 4 may be provided with a vent toprevent excessive pressure buildup. Some silicon tetrafiuoride will tendto escape through such vent, but to a considerable degree theself-regenerating feature of the structure of FIG. 4 is retained.

in any of the devices made in accordance with the present invention itis necessary that the quantity of silicon tetrafiuoride evolved to besuflicient in relation to the arcing space to provide the necessarydielectric strength. That is, when the arc is interrupted, the siliconIt will be noted that in each of the devices here shown and described apair of spaced electrode faces are provided between which an arc extendsprior to interruption. The metal silico-fiuoride is located onsomeportion of the mechanism exposed to the action of the arc. As shownby the respective embodiments, the location of the silicofluoridematerial maybe varied as desired so long as it is acted upon by the are.

While we have shown and described particular er'nbodi-i ments of thepresent invention it will, of course, be understood that variousmodifications and alternative constructions may be made withoutdeparting from its true spirit and scope. The invention may, forexample, be applied to fuses for high voltage interruption, air circuitbreakers where the arc is magnetically or otherwise driven ontodeionizing means such as arc-chutes and the like (which may include anon-conducting metallic silico-fiuoride double salt to generate silicontetrafiuoride) and in other similar applications. We therefore intend bythe appended claims to cover all such modifications and alternativeconstructions as fall within their true spirit and scope. a

What We claim as new and desire to secure by Letters Patent of theUnited States is:

4. A surge voltage protector comprising in combination: a pair of spacedelectrodes with arcing faces defining an arc-space to be spanned by anarc prior to inter-.

ruption; and means locatedwithin' the zone of thermal influence of thearc and including a metal siltco-fiuoride material which when exposed toarc current fiow generates silicon tetrailuoride gas that momentarilyoccupies the arc-space to provide a mediumof rapid dielectric strength 7recovery upon arc extinction, I V 5. A surge voltage protectorcomprising in combination: a pair of spaced electrodes defining anarc-space between which an arc is'struck upon application ofpredetermined surge voitage; and means located within the zone ofthermal influence of the arc and including a metal silico-fiuoridematerial which when exposed to are current flow generates silicontetrafluoride gas that momentarily occupies the arc-space to provide amedium of determined surge voltage; and insulating means sustain- 1. Acircuit interrupter comprising'in combination: means defining asubstantially enclosed chamber; a pair of spaced electrodes within thechamber defining an arcthat momentarily occupies said arc-space toprovide a medium of rapid dielectric strength recovery upon arcextinction, the gas further recombining with residual material withinthe chamber over a period of time to regenerate metal silico-fluorideand to condition the interrupter for future interruptions.

2. A circuit interrupter comprising in combination: means defining asubstantially enclosed chamber; and a pair of spaced electrodes withinthe chamber defining an arc-space to be spanned by an arc prior tointerruption, at least one of the electrodes defining an arcing surfaceand containing a metal silico-fiuoride which upon heating by said arcgenerates silicon tetrafiuoride gas that momentarily occupies thearc-space to provide a medium of rapid dielectric strength recovery uponarc extinction, the gas further recombining with the residual electrodematerial over a period of time to regenerate metal silicofluoride and tocondition theinterrupter for future interruptions. 3. A circuitinterrupter comprising in combination:

ing the electrodes in spaced relation and located within the Zone ofthermal influence of the arc, said insulating means including surfaceshaving a metal silico-fiuoride material which when heated by arc currentflow generates recovery upon arc extinction. I

- 7. A current interrupter comprising in combination: a pair ofspacedelectrodeswith.arcingfaces defining an arc-space to be spanned by an arcprior to interruption,

at least one of the arcing faces including a metal silicofluoridematerial which when heated by arc current flow generatessilicontetrafiuoride gas that momentarily occupies the arc-space toprovide a medium of rapid dielectric strength recovery upon arcextinction.

8. A circuit interrupter comprisingin combination: a

first means defining an electrode face; a second means defining anelectrode face;-and third means supporting tion, at least one of saidmeans having portions exposed means defining a substantially enclosedchamber; means including a pair of spaced electrodes with arcing facesdefining an arc-space to be occupied by anarc prior to 1 interruption,said means defining substantially the only exposed metal in the chamberand having at least a region adjacent one face comprising a metalsilico-fluoride material which upon heating by said are generatessilicon to regenerate metal silico-fluoride and to condition theinterrupter for future interruption.

to the action of the arc andincluding a metal silicofluoride. V 9. Acircuit interrupter comprising in combination: a firstmeans defining anelectrode faceya second means defining an electrode face; and thirdmeans supporting said first and second means in spaced relationto definean arc-space to be occupied by an arc prior to interrup- 'tion, at leastone of said meansdefining portions containing cuprous silico-fiuorideand exposed to the action of the are.

10. A circuit interrupter comprising in combination: a

first means defining an electrode face; a second means defining anelectrode face; and third means supporting said first and second meansinspaced relation to define an arc-space to be occupied by an arc prior tointerrup tion, at least one of said means including portions glazed witha material including a metal silico-fluoride' andexposed to the actionof the arc.

References Cited in the tile of this patent UNITED STATES PATENTS2,279,040 Grosse Apr. 7, 1942 2,352,984 Walle July 4, 1944 2,596,967Frost May 20, 1952 2,832,669 Allen Apr. 29, 1958

1. A CIRCUIT INTERUPTER COMPRISING IN COMBINATION: MEANS DEFINING ASUBSTANTIALLY ENCLOSED CHAMBER; A PAIR OF SPACED ELECTRODES WITHIN THECHAMBER DEFINING AN ARCSPACE TO BE SPANNED BY AN ARC PRIOR TOINTERUPTION; AND